Winter is poised to make a frontal assault on the U.S.

Once every so often, the United States has one of those memorable winters. One of those winters where a weather pattern locks bitterly cold arctic air over much of the country for an extended period of the December to February period. Winters like 1918 (famous for the deadly flu), 1936, any of the winters in the late 70's, 1982 or 1994 are all remembered for long and very extreme outbreak's of bitterly cold air. Vermonters are probably not ready to award this distinction to the 2014 winter as of yet since much of the brunt of the cold and anomalous snow has been focused on the center of the country. But for another upcoming 10 day stretch, the central and eastern parts of the country will again be the focal point for another extended period of extreme cold. This will occur thanks the development of a very powerful blocking ridge in the jet stream extending from the western United States northward to the Yukon. This is one of the more impressive blocking features we have seen in this region going back at least a decade ,and it occurs in a year when the pooling efficiency of air masses in the polar regions has been particularly impressive. By the end of the month, January 2014 and perhaps the entire winter will be remembered as one of the coldest in a generation. Strong language, but well earned given the temperatures we are likely going to have to endure.

The presence of the polar jet over New England and the rest of the country is reeking havoc on the performance of the models. We have gotten some good indications regarding the general pattern evolution but the details have proven almost impossible to pin down. Storms will show up on a model run for the weekend and then disappear a day later. Another model might snow a big snow event for early next week and that storm will later vanish on a subsequent model run. To put it as plainly as possible, the polar jet operates in a different gear. Impulses rotate through the jet so quickly and the models have a hard time digesting what impact, if any, they will have on actual weather.  In other words, we have and will continue to be teased now and again and a storm might sneak up on us very late in a forecast period.

For now, it seems like there is some consensus on the weekend. Temperatures will stay in a very tolerable range, climbing to near 30 both Saturday and Sunday and only falling into the teens. Enjoy it because beyond that lies an abyss of brutally cold weather for New England. We will also get some snow this weekend. Two clipper systems are responsible for this. The first was the one we had hoped would ultimately bomb-out along the coast delivering lots of snow; instead, we should see a period of light snow Saturday evening into the overnight amounting hopefully to a few inches. On Sunday a clipper will rapidly advance southeast out of Ontario on the wings of the arriving polar jet. This system will deliver another few inches of snow Sunday night. Flurries will continue into Monday but the story for the rest of the week will be cold, brutal cold. Temperatures for much of the week will be below zero on the mountain including readings lower than 10 below in the morning and day time temperatures that struggle to get above zero. We have been teased and may continue to be teased with a potential storm around the time of Friday/Saturday the 24th/25th. I think this system has the potential to be more than just a tease but time will tell.

The ultra positive PNA will continue to support the bitterly cold temperatures until at least the 28th of January and then it gets interesting. The strength of the ridge in the Yukon will relax and there are signs of some serious splitting in the jet stream in the Pacific. This is the kind of situation that can lead to big time snow events for both New England and many other places.